patch 8.1.1956: screenshot tests may use a different encoding

Problem:    Screenshot tests may use a different encoding. (Dominique Pelle)
Solution:   Always set 'encoding' to "utf-8" when running Vim in a terminal.
            (closes #4884)
diff --git a/src/version.c b/src/version.c
index afde7b6..5c29e3c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1956,
+/**/
     1955,
 /**/
     1954,